D is for Demanding

Excitement surrounds new deep mine development at Kidd

Excitement is growing in Timmins, Ont. The world’s deepest base metal mine is under development by Falconbridge Ltd.’s Kidd Mining Division. Its christening as “Mine D” (for deep) is well justified.

The Kidd mine celebrates its 35th birthday this year, and Mine D has the potential to ensure it reaches 60 years. It is to be developed in two stages. Reserves outlined for Stage I mining are 15.7 million tonnes grading 2.82% Cu, 5.74% Zn and 58 g/t Ag. Stage II will recover an additional 10.5 million tonnes at 2.20% Cu, 5.27% Zn and 97 g/t Ag. Production will begin in 2004 and peak at 2.0 million tonnes per year in 2013.

This much-needed new reserve will replace ore from the three existing mines as they are depleted. The No.2 mine will be exhausted in the next two years, then the No.1 mine in 2007. The No.3 mine has reserves that will last until 2013. But Mine D will go on until at least 2024.

Mining to the tremendous depth of 3,200 metres (10,500 feet) can be undertaken only after consideration of all the risks and very careful planning. In 1996, Kidd planners met with deep mining experts from around the world. Based on the input of these specialists and the considerable skills of its own people, Falconbridge is confident that Mine D will be not only a technical success, but a profitable one as well.

“There have been four years of solid work,” engineering manager Rick Howes told CMJ. “I’ve worked on other projects before, but there’s more up-front work done on this one than any I have ever seen.”

That intense study and planning led to the official green light on July 19, 2000.

The company’s confidence in Mine D is founded on a precise timetable and strict budget. From beginning the ramp last August, to Stage I production in 2004 and Stage II production in 2009, each step of the way is clearly defined. It has to be, to stay within the budget of $640 million. It’s a budget that makes Mine D probably the largest single underground development in Canada.

Of the $510 million allocated to Stage I (with contingency), sinking an internal shaft will eat up $131 million. Overhauling the ventilation system and adding a large refrigeration plant will cost $42 million. Pre-production development will cost $89 million, and $35 million is set aside to purchase new underground mobile equipment. A new paste fill system will cost $19 million. There is an additional $128 million required for rock sizing and handling, dewatering and other site services and facilities. Stage II development is expected to cost an additional $77 million.

New Ramp and Shaft

Driving the new 5.1-m by 5.l- m ramp from 68 Level (2,100 metres) has already begun. Running at a gradient of 15% it will eventually reach a depth of 3,100 metres.

The shaft-sinking contract is to be let this month. It calls for a 7.62-m-diameter, concrete-lined winze running from 47 Level (1,430 metres, and the current lowest working level) to 105 Level (3,200 metres below surface). When production begins there will be five compartments. Two will handle the 20-tonne skips. One will hold the 128-person double deck cage. The fourth will be used for an auxiliary cage. Piping and services will run through the remaining compartment.

Three new hoists will be installed. For skipping, a 5.5-m-diameter, double drum, 4,500-kW machine is specified. The main cage will be handled by a similar 2,500-kW hoist. The third will be a 2.7-m diameter, single drum, 450-kW hoist for the auxiliary cage. The rope gallery for the hoists will be constructed horizontally on 44 Level, where the main hoist rooms will be built. The hoistmen will work remotely from a control centre on surface.

Falconbridge expects the new hoists to be delivered in October this year. Sinking can then begin in April 2002 and continue to the end of 2006. Beginning in 2004, sinking and production will take place simultaneously. A cage and a skip will occupy the two skip compartments during the sinking period to allow for development of the shaft and early production during sinking. The shaft-sinking contractor will have the use of the main cage compartment and the auxiliary cage compartment.

As mining proceeds in five oreblocks, three jaw crushers will be installed. For the most part, the crushing stations will be unmanned and remotely controlled.

Ventilation and Refrigeration

Developing Mine D presents the opportunity to update the ventilation system for all the mines. The system is to be completely overhauled beginning with a ventilation shaft (already started) from surface to 490 metres depth, where it will connect with the existing system. A concrete-lined shaft 2.1-m in diameter will be built.

The new ventilation strategy will deliver energy savings as well as fresh air. Ventilation accounts for 60% of energy costs at Kidd. There are over 200 main fans in a push-pull configuration currently drawing over 11,000 kW of power. After the changes are made, there will be only five main fans–three units on surface and two boosters underground–which will ultimately draw over 50% less power than the current push-pull configuration. With the addition of automated on-demand operation monitored from a central control room, Howes calls the potential savings “terrific”.

Another consideration in deep mining is heat. The ambient temperature must be kept under 28C WBGT (wet bulb global temperature) for the workers. Although rock temperatures in the Timmins area are typically at least 15C cooler than many other regions such as the Sudbury basin, they are still predicted to be 35C at a depth of 3,000 metres in Mine D. A massive refrigeration plant is the only answer.

The first stage of the installation will be operational in 2004, another will come on stream two years later, and a third in 2008. The plant will use compressors, condensers, evaporators and ammonia to indirectly cool water, which will in turn be used to cool the intake air for the mine. This indirect method is necessary to protect underground workers from fumes should the plant ever develop an ammonia leak. The cooling plant will produce 17 MWR (megawatts refrigeration) of cooling capacity for the mine.

Ground Control and Mining

Kidd engineers believe that advanced ground control at depth will make mining no riskier than in the existing operations closer to surface. Spray-on lining will eliminate the need for screen and will improve the ground support quality and efficiency of the development. Uniform lining thickness is needed and will be possible using new robotic shotcrete sprayers.

Ore will be recovered from Mine D using a fine-tuned version of open blasthole stoping, which is practised in the shallower mines. Geotechnical modelling indicates that the preferred stope size will be larger (60,000-tonnes) than in the current No.3 mine (40,000-tonnes). Stopes will be paste filled to allow later pillar recovery. The ore is known to be pyrophoric, oxidizing and releasing SO2 when freshly broken. This requires thorough ventilation after blasting, but is not a problem in established openings.

Large stopes require a fleet of large equipment. This will likely be 7.6- to 9-m3 (10-12 cu. yd.) load-haul-dumpers and 40-t and 50-tonne trucks. Where new technologies might reduce maintenance and increase productivity, they are being evaluated. Innovations such as self-digging LHDs, automated jumbos, automated cable bolters and the aforementioned robotic Shotcrete sprayer are of interest.

State-of-the-art infrastructure is also in the design for Mine D. High bandwidth, fibre optic communications will carry video and data streams as well as voice. New cap lamps with integrated radios are a possibility. And new methods of notifying underground employees in case of emergency are being sought.

Forming the Future

Developing Mine D will require approximately 250 to 300 people onsite during the peak construction period 2001-2004. Most of this work will be completed with the use of contractors. The manpower levels required to operate the mine once the const
ruction is completed are balanced fairly well with the normal attrition that occurs at the mine. New jobs in the deep workings will replace those being lost with the closing of the other mines.

Maintaining employment is only one benefit of Mine D. The other, and it is a big one, is to secure a local feed supply for the Kidd copper smelter and zinc refinery, also in Timmins. Today, a metallurgical complex of this size perhaps would not be built where transportation adds much to costs. But the facility is there, and it is among the most technically advanced in the world. Copper concentrate from external sources, particularly the Collahuasi mine in Chile, now provides more feed for the smelter than local sources. The cost of concentrate and freight shipping to and from northern Ontario adds to operating costs. Naturally, the availability of ore from Mine D will relieve those costs.

Mine D excitement has touched not only Timmins but also Falconbridge executives in Toronto. Warren Holmes, senior VP of Canadian mining operations, looks at the challenges–of depth, heat, geomechanics, logistics, backfilling, and ventilation–and tells CMJ he is “pretty pleased with this venture.”

So are a lot of people.

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